石化廠環狀高壓蒸氣管網之建模與分析研究

Abstract

本研究由直管與管件個別之質量、動量與能量守恆方程式出發，先探討各元件之功能與其對於蒸氣出口溫度與壓力之影響，進而將其推展至單管蒸汽系統，由各元件之影響來探討其對於溫度與壓力分布之改變。 於環狀網路之研究中，我們採用哈迪•克勞斯法，在嘗試應用哈迪•克勞斯法於水網路之後，我們將其理念與先前之單管蒸汽系統合併，推導出修改過之哈迪•克勞斯法，修改過之哈迪•克勞斯法藉由平均物性與壓力平衡為主要理念，搭配上熱散失與相變化之計算，修改過後之哈迪•克勞斯法適用於含有溫降之可壓縮流體系統中，本研究將此法應用於環狀蒸汽管網之分析。 最後，本研究以修改過之哈迪•克勞斯法來針對大型石化廠之環狀高壓蒸氣管網做分析，此章節探討當煉油廠內某個蒸汽供應單元維修或故障時，不同蒸汽調度策略對於系統之影響，其結果顯示當調度策略不當時將會造成系統中產生管網冷點與單元冷點，本研究提供一種預測之模型，可用以避免管網冷點與單元冷點之現象，亦可用於模擬各種不同架構間之優劣。

This thesis star from straight pipe and fitting with mass, momentum and energyconservation equations to calculate ressure drop and temperature drop of these straight pipe and fitting. Single pipeline system is solved by combined with straight pipes and fittings. By using temperature, pressure and condensate profile, the influence of each straight pipe and fitting are observed. Base on the result of single pipeline system, Hardy-Cross method is modified to deal with steam distribution on looped pipe network. The modified Hardy-Cross method is using pressure balance as main criteria and the density of fluid is variable. Via three cases to prove that modified Hardy-Cross method is usable. Finally, a large-scale refinery is solved by using modified Hardy-Cross method. Three different scenarios and two different strategies are proposed to deal with one of boiler repairing. Via modified Hardy-Cross method, cool points of each scenario and each strategy are indicated. The modified Hardy-Cross method can using to predict steam flow rate and direction in looped steam pipe network. Moreover, via modified Hardy-Cross method, the phenomena of switch of flow direction is found. It can demonstrate situations of cool points and cool units and propose best operating strategy to avoid cool points and cool units.